<?php
/**
 * Class Minify_HTML
 * @package Minify
 */

/**
 * Compress HTML
 *
 * This is a heavy regex-based removal of whitespace, unnecessary comments and
 * tokens. IE conditional comments are preserved. There are also options to have
 * STYLE and SCRIPT blocks compressed by callback functions.
 *
 * A test suite is available.
 *
 * @package Minify
 * @author Stephen Clay <steve@mrclay.org>
 */
class Minify_HTML {

	/**
	 * "Minify" an HTML page
	 *
	 * @param string $html
	 *
	 * @param array $options
	 *
	 * 'cssMinifier' : (optional) callback function to process content of STYLE
	 * elements.
	 *
	 * 'jsMinifier' : (optional) callback function to process content of SCRIPT
	 * elements. Note: the type attribute is ignored.
	 *
	 * 'xhtml' : (optional boolean) should content be treated as XHTML1.0? If
	 * unset, minify will sniff for an XHTML doctype.
	 *
	 * @return string
	 */
	public static function minify($html, $options = array()) {
		$min = new Minify_HTML($html, $options);
		return $min->process();
	}


	/**
	 * Create a minifier object
	 *
	 * @param string $html
	 *
	 * @param array $options
	 *
	 * 'cssMinifier' : (optional) callback function to process content of STYLE
	 * elements.
	 *
	 * 'jsMinifier' : (optional) callback function to process content of SCRIPT
	 * elements. Note: the type attribute is ignored.
	 *
	 * 'xhtml' : (optional boolean) should content be treated as XHTML1.0? If
	 * unset, minify will sniff for an XHTML doctype.
	 *
	 * @return null
	 */
	public function __construct($html, $options = array())
	{
		$this->_html = str_replace("\r\n", "\n", trim($html));
		if (isset($options['xhtml'])) {
			$this->_isXhtml = (bool)$options['xhtml'];
		}
		if (isset($options['cssMinifier'])) {
			$this->_cssMinifier = $options['cssMinifier'];
		}
		if (isset($options['jsMinifier'])) {
			$this->_jsMinifier = $options['jsMinifier'];
		}
	}


	/**
	 * Minify the markeup given in the constructor
	 *
	 * @return string
	 */
	public function process()
	{
		if ($this->_isXhtml === null) {
			$this->_isXhtml = (false !== strpos($this->_html, '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML'));
		}

		$this->_replacementHash = 'MINIFYHTML' . md5($_SERVER['REQUEST_TIME']);
		$this->_placeholders = array();

		// replace SCRIPTs (and minify) with placeholders
		$this->_html = preg_replace_callback(
            '/(\\s*)(<script\\b[^>]*?>)([\\s\\S]*?)<\\/script>(\\s*)/i'
            ,array($this, '_removeScriptCB')
            ,$this->_html);

            // replace STYLEs (and minify) with placeholders
            $this->_html = preg_replace_callback(
            '/\\s*(<style\\b[^>]*?>)([\\s\\S]*?)<\\/style>\\s*/i'
            ,array($this, '_removeStyleCB')
            ,$this->_html);

            // remove HTML comments (not containing IE conditional comments).
            $this->_html = preg_replace_callback(
            '/<!--([\\s\\S]*?)-->/'
            ,array($this, '_commentCB')
            ,$this->_html);

            // replace PREs with placeholders
            $this->_html = preg_replace_callback('/\\s*(<pre\\b[^>]*?>[\\s\\S]*?<\\/pre>)\\s*/i'
            ,array($this, '_removePreCB')
            ,$this->_html);

            // replace TEXTAREAs with placeholders
            $this->_html = preg_replace_callback(
            '/\\s*(<textarea\\b[^>]*?>[\\s\\S]*?<\\/textarea>)\\s*/i'
            ,array($this, '_removeTextareaCB')
            ,$this->_html);

            // trim each line.
            // @todo take into account attribute values that span multiple lines.
            $this->_html = preg_replace('/^\\s+|\\s+$/m', '', $this->_html);

            // remove ws around block/undisplayed elements
            $this->_html = preg_replace('/\\s+(<\\/?(?:area|base(?:font)?|blockquote|body'
            .'|caption|center|cite|col(?:group)?|dd|dir|div|dl|dt|fieldset|form'
            .'|frame(?:set)?|h[1-6]|head|hr|html|legend|li|link|map|menu|meta'
            .'|ol|opt(?:group|ion)|p|param|t(?:able|body|head|d|h||r|foot|itle)'
            .'|ul)\\b[^>]*>)/i', '$1', $this->_html);

            // remove ws outside of all elements
            $this->_html = preg_replace_callback(
            '/>([^<]+)</'
            ,array($this, '_outsideTagCB')
            ,$this->_html);

            // use newlines before 1st attribute in open tags (to limit line lengths)
            $this->_html = preg_replace('/(<[a-z\\-]+)\\s+([^>]+>)/i', "$1\n$2", $this->_html);

            // fill placeholders
            $this->_html = str_replace(
            array_keys($this->_placeholders)
            ,array_values($this->_placeholders)
            ,$this->_html
            );
            return $this->_html;
	}

	protected function _commentCB($m)
	{
		return (0 === strpos($m[1], '[') || false !== strpos($m[1], '<!['))
		? $m[0]
		: '';
	}

	protected function _reservePlace($content)
	{
		$placeholder = '%' . $this->_replacementHash . count($this->_placeholders) . '%';
		$this->_placeholders[$placeholder] = $content;
		return $placeholder;
	}

	protected $_isXhtml = null;
	protected $_replacementHash = null;
	protected $_placeholders = array();
	protected $_cssMinifier = null;
	protected $_jsMinifier = null;

	protected function _outsideTagCB($m)
	{
		return '>' . preg_replace('/^\\s+|\\s+$/', ' ', $m[1]) . '<';
	}

	protected function _removePreCB($m)
	{
		return $this->_reservePlace($m[1]);
	}

	protected function _removeTextareaCB($m)
	{
		return $this->_reservePlace($m[1]);
	}

	protected function _removeStyleCB($m)
	{
		$openStyle = $m[1];
		$css = $m[2];
		// remove HTML comments
		$css = preg_replace('/(?:^\\s*<!--|-->\\s*$)/', '', $css);

		// remove CDATA section markers
		$css = $this->_removeCdata($css);

		// minify
		$minifier = $this->_cssMinifier
		? $this->_cssMinifier
		: 'trim';
		$css = call_user_func($minifier, $css);

		return $this->_reservePlace($this->_needsCdata($css)
		? "{$openStyle}/*<![CDATA[*/{$css}/*]]>*/</style>"
		: "{$openStyle}{$css}</style>"
		);
	}

	protected function _removeScriptCB($m)
	{
		$openScript = $m[2];
		$js = $m[3];

		// whitespace surrounding? preserve at least one space
		$ws1 = ($m[1] === '') ? '' : ' ';
		$ws2 = ($m[4] === '') ? '' : ' ';

		// remove HTML comments (and ending "//" if present)
		$js = preg_replace('/(?:^\\s*<!--\\s*|\\s*(?:\\/\\/)?\\s*-->\\s*$)/', '', $js);

		// remove CDATA section markers
		$js = $this->_removeCdata($js);

		// minify
		$minifier = $this->_jsMinifier
		? $this->_jsMinifier
		: 'trim';
		$js = call_user_func($minifier, $js);

		return $this->_reservePlace($this->_needsCdata($js)
		? "{$ws1}{$openScript}/*<![CDATA[*/{$js}/*]]>*/</script>{$ws2}"
		: "{$ws1}{$openScript}{$js}</script>{$ws2}"
		);
	}

	protected function _removeCdata($str)
	{
		return (false !== strpos($str, '<![CDATA['))
		? str_replace(array('<![CDATA[', ']]>'), '', $str)
		: $str;
	}

	protected function _needsCdata($str)
	{
		return ($this->_isXhtml && preg_match('/(?:[<&]|\\-\\-|\\]\\]>)/', $str));
	}
}
